1. Field of the Invention
The present invention relates to a liquid discharge head for discharging liquid by creating a bubble (bubbles) with thermal energy acting upon liquid, and the method of manufacture therefor. The invention also relates to a liquid discharge apparatus that uses such liquid charge head.
Also, the present invention is applicable to a printer that records on a recording medium, such as paper, thread, fabric, cloth, leather, metal, plastic, glass, wood, ceramic, a copying machine, a facsimile equipments provided with communication system, and a word processor having a printing unit therefor. The invention further relates to an industrial recording apparatus formed complexly in combination with various processing apparatuses.
In this respect, the term xe2x80x9crecordingxe2x80x9d referred to in the specification of the invention hereof not only means the provision of characters, graphics, and other meaningful images for a recording medium, but also, means the provision of images, such as patterns, which are not meaningful.
2. Related Background Art
Conventionally, for the so-called bubble jet recording method has been known, which is an ink jet recording method for forming images by the adhesion of ink onto a recording medium by discharging ink from discharge ports by the acting force based upon the abrupt voluminal changes following the creation of bubble by applying thermal energy or the like to liquid ink in flow paths of a recording apparatus, such as a printer. As disclosed in the specification of the U.S. Pat. No. 4,723,129, the recording apparatus that uses this bubble jet recording method is generally provided with discharge ports to discharge ink; flow paths communicated with these discharge ports; and electrothermal converting elements arranged in the flow paths to serve as energy generating means.
In accordance with a recording method of the kind, it becomes possible to record high quality images at high speeds in a lesser amount of noises, and at the same time, to arrange discharge ports for discharging ink in high density for the head using this recording method with such an excellent advantage, among some others, that recorded images are obtained in high resolution even in colors with a smaller apparatus. Therefore, the bubble jet recording method has been widely utilized for a printer, a copying machine, a facsimile equipment, and other office equipment in recent years. Further, this method has been utilized even for an industrial system, such as a textile printing apparatus.
Along with the wider utilization of bubble jet technologies and techniques for the products in various fields, there are increasingly more demands in various aspects. Then, for example, in order to obtain higher quality images, there has been proposed the driving condition whereby to provide a liquid discharge method or the like that performs excellent ink discharges at higher speeds based upon the stabilized creation of bubble or in consideration of the achievement of higher recording, there has been proposed the improved flow path configurations for obtaining a liquid discharge head having a higher refilling speed of liquid into the liquid flow path where liquid has been discharged.
Of these proposals, for the head that discharges liquid along with the growth and shrinkage of bubble created in nozzles, it has been known that the efficiency of discharge energy and the refilling characteristics of liquid tend to become unfavorably by the bubble growth in the direction opposite to the corresponding discharge port, and the resultant liquid flow caused thereby. The invention of a structure in which to enhance the discharge energy efficiency, as well as the refilling characteristics of the kind has been proposed in the specification of the European Patent Laid-Open Application EP-0436047A1.
The invention disclosed in the specification of this European Laid-Open Application is such that a first valve that cuts off the connection between the area near the discharge port and the bubble generating area, and a second valve that cuts off the connection between the bubble generating area and the ink supply portion completely, and that these valves are open and closed alternately (see FIG. 4 to FIG. 9 of the EP436047A1). For example, in accordance with the example shown in FIG. 7 of the aforesaid Laid-Open Application, a heat generating element 110 is arranged substantially in the center of the ink flow path 112 between the ink tank 116 and the nozzle 115 on the base plate 125 that forms the inner wall of the ink flow path 112 as shown in FIG. 37 hereof. The heat generating element 110 resides in the section 120 which closes all the circumferences in the interior of the ink flow path 112. The ink flow path 112 comprises the base plate 125; the thin films 123 and 126 which are laminated directly on the base plate 125; and tongue pieces 113 and 130 serving as closing devices. The tongue pieces in releasing condition are indicated by broken lines in FIG. 37. The other thin film 123 which extends on the flat plane parallel to the base plate 125 and terminates by the stopper 124 is arranged to shield over the ink flow path 112. When a bubble is created in ink, the free end of the tongue piece 130 on the nozzle region, which is in contact with the stopper 124 in its stationary condition, is displaced toward upward. Thus, ink liquid is discharged from the section 120 into the ink flow path 112, and discharged through the nozzle 115. At this juncture, the tongue piece 113, which is arranged in the area of the ink tank 116, is closely in contact with the stopper 124 in the stationary condition. Therefore, there is no possibility that ink liquid in the section 120 is directed to the ink layer 116. When the bubble in ink is extinct, the tongue piece 130 is displaced downward, and it is again closely in contact with the stopper 124. Then, the tongue piece 113 falls down in the ink section 120, thus allowing ink liquid to flow into the section 120.
However, in accordance with the invention described in the specification of the EP436047A1, the three chambers for the area near the discharge port, the bubble generating portion, and the ink supply portion are divided into two each. Therefore, ink that follows the ink droplet becomes a long tail when discharged, and satellites may ensue inevitably more than the usual method of discharge where the growth, shrinkage, and extinction of bubble are carried out (presumably, because the effect of the meniscus retraction that may be produced by the bubble extinction is not usable). Also, the valve on the discharge port side of the bubble tends to invite a great loss of discharge energy. Moreover, at the time of refilling (when ink is replenished for the nozzle), liquid cannot be supplied to the area near the discharge port until the next bubbling takes place, although liquid is supplied to the bubble generating portion along with the extinction of bubble. As a result, not only the fluctuation of discharged droplets is greater, but the frequency of discharge responses becomes extremely smaller, hence making this method far from being practicable.
With the present invention, it is intended to propose the devise to enhance the discharge efficiency satisfactorily based upon a new idea whereby to find an epoch-making method and head structure by improving the efficiency of suppression of the bubble growing component in the direction opposite to the discharge port, while satisfying the higher enhancement of the refilling characteristics, which is directly-opposed idea of providing more suppression on such component of growing bubble on the opposite side of the discharge port.
As a result of the assiduous studies made by the inventors hereof, it has been found to be able to utilize the discharge energy directed backward on the discharge port side effectively by means of check-valve mechanism specially constructed in the nozzle structure of a liquid discharge head that discharges liquid along with the growth of bubble created in the nozzle which is linearly formed. Here, with the special check-valve mechanism, the growing component of bubble directed backward is suppressed, and at the same time, the refilling characteristics are made more efficient. It has been found then that the frequency of discharge responses is made higher significantly.
In other words, it is an object of the present invention to establish a new discharging method (structure) whereby to attain a head capable of obtaining the high quality images at high speed, which have never been obtainable with the conventional art, with the nozzle structure and discharging method that use a novel valve mechanism.
The liquid discharging method of the present invention obtained in the process of the aforesaid studies of the liquid head discharge head, which is provided with a plurality of discharge ports for discharging liquid; a plurality of liquid flow paths communicated always with each of the discharge ports at one end, each having bubble generating area for creating bubble in liquid; bubble generating means for generating energy to create and grow the bubble; a plurality of liquid supply ports each arranged for each of the liquid flow paths to be communicated with common liquid supply chamber; and movable member supported with minute gap to the liquid supply port on the liquid flow path side, and provided with free end, the area of the movable member surrounded at least by the free end portion and both sides continued therefrom being made larger than the opening area of the liquid supply port facing the liquid flow path, comprises the step of setting a period for the movable member to close and essentially cut off the opening area during the period from the application of driving voltage to the bubble generating means to the substantial termination of isotropical growth of the entire bubble by the bubble generating means.
Also, for the aforesaid liquid discharging method, the period for the movable member to close and essential cut off the opening area continues at least until the termination of the period of substantially isotropical growth of the entire bubble by the bubble generating means.
Further, for the aforesaid liquid discharging method, during the growing period of the portion of the bubble created by the bubble generating means on the discharge port side after the period for the movable member to close and substantially cut off the opening area, the movable member begins to be displaced from the position of closing and substantially cutting off the opening area to the bubble generating means side in the liquid flow path, and makes liquid supply possible from the common liquid supply chamber to the liquid flow path.
Further, after the movable member begins to be displaced from the position of closing and substantially cutting off the opening area to the bubble generating means side in the liquid flow path, the movable member is further displaced to the bubble generating means side during the shrinking period of the portion of the bubble on the movable member side to supply liquid from the common liquid supply chamber to the liquid flow path.
Further, the voluminal changes of bubble growth and the period from the generation of bubble to the extinction thereof on the bubble generating area are different largely on the discharge port side and the liquid supply port side.
The liquid discharge head of the present invention comprises a plurality of discharge ports for discharging liquid; a plurality of liquid flow paths communicated always with each of the discharge ports at one end, each having bubble generating area for creating bubble in liquid; bubble generating means for generating energy to create and grow the bubble; a plurality of liquid supply ports each arranged for each of the liquid flow paths to be communicated with common liquid supply chamber; and movable member supported with minute gap of 10 xcexcm or less to the liquid supply port on the liquid flow path side, and provided with free end, the area of the movable member surrounded at least by the free end portion and both sides continued therefrom being made larger than the opening area of the liquid supply port facing the liquid flow path, and the discharge port and the bubble generating means being in linearly communicative state.
Also, the liquid discharge head of the present invention comprises a discharge port for discharging liquid; a liquid flow path communicated always with the discharge port at one end, having bubble generating area f or creating bubble in liquid; bubble generating means for generating energy to create and grow the bubble; a liquid supply port arranged for the liquid flow path to be communicated with common liquid supply chamber; and movable member supported with minute gap of 10 xcexcm or less to the liquid supply port on the liquid flow path side, and provided with free end, the area of the movable member surrounded at least by the free end portion and both sides continued therefrom being made larger than the opening area of the liquid supply port facing the liquid flow path, and the discharge port and the bubble generating means being in linearly communicative state.
For these liquid discharge heads, it is preferable to provide the movable member also with gaps to with flow path walls forming the liquid flow path.
Also, the liquid discharge head of the present invention comprises a plurality of discharge ports for discharging liquid; a plurality of liquid flow paths communicated always with each of the discharge ports at one end, each having bubble generating area for creating bubble in liquid; bubble generating means for generating energy to create and grow the bubble; a plurality of liquid supply ports each arranged for each of the liquid flow paths to be communicated with common liquid supply chamber; and movable member supported with minute gap to the liquid supply port on the liquid flow path side, and provided with free end, the area of the movable member surrounded at least by the free end portion and both sides continued therefrom being made larger than the opening area of the liquid supply port facing the liquid flow path, and having a period for the movable member to close and essentially cut off the opening area during the period of substantially isotropical growing of the entire bubble by the bubble generating means on the discharge port side after the application of driving voltage to the bubble generating means, and the movable member beginning to be displaced from the position of closing and essentially cut off the opening area to the bubble generating means side in the liquid flow path during the period of the portion of bubble created by the bubble generating means on the discharge port side being grown after the period of the same movable member to close and essentially cut off the opening area, making liquid supply possible from the common liquid supply chamber to the liquid flow path. For this liquid discharge head, given the maximum volume of bubble growing in the bubble generating area on the discharge port side as Vf, and given the maximum volume of bubble growing in the bubble generating area on the liquid supply port side as Vr, the relationship of Vf greater than Vr is established at all times.
In this case, given the life time of bubble growing in the bubble generating area on the discharge port side as Tf, and given the life time of bubble growing in the bubble generating area on the liquid supply port side as Tr, the relationship of Tf greater than Tr is established at all times.
Then, the point of the bubble extinction is positioned on the discharge port side from the central portion of the bubble generating area.
Also, the liquid discharge head of the present invention comprises a plurality of discharge ports for discharging liquid; a plurality of liquid flow paths communicated always with each of the discharge ports at one end, each having bubble generating area for creating bubble in liquid; bubble generating means for generating energy to create and grow the bubble; a plurality of liquid supply ports each arranged for each of the liquid flow paths to be communicated with common liquid supply chamber; and movable member supported with minute gap to the liquid supply port on the liquid flow path side, and provided with free end, the area of the movable member surrounded at least by the free end portion and both sides continued therefrom being made larger than the opening area of the liquid supply port facing the liquid flow path, and the free end of the movable member being minutely displaced in the liquid flow path to the liquid supply port side in the initial stage of the bubble creation, and along with the bubble extinction, the free end of the movable member is largely displaced in the liquid flow path to the bubble generating means side for supplying liquid from the common liquid supply chamber into the liquid flow path through the liquid supply port.
In this case, the amount of displacement of the free end of the movable member is defined as h1 as the amount of displacement in the liquid flow path to the liquid supply port side in the initial stage of the bubble creation, and when the free end of the movable member is displaced in the liquid flow path to the bubble generating means side along with the bubble extinction, the amount of displacement thereof is defined as h2, and then, the relationship of h1 less than h2 is established at all times.
For each of the aforesaid liquid discharge heads, thin film of amorphous alloy is provided for the uppermost surface of the bubble generating means. Then, it is conceivable that the aforesaid amorphous alloy is an alloy of at least one metal or more selected from tantalum, iron, nickel, chromium, germanium, ruthenium.
Further, for the aforesaid liquid discharge head, it is preferable to integrally form the food supporting member with the movable member to support the foot of the movable member, and provide such member with a step for deviating the height position of the movable member by one step to the fixing position of the foot supporting member, and to make the thickness of the movable member larger than the amount of such step.
Further, it is preferable to arrange the relationship between a gap xcex1 between the opening edge of the liquid supply port on the liquid flow path side and the face of the movable member on the liquid flow supply port side, and the overlapping width W3 of the movable member in the widthwise direction overlapping with the opening edge of the liquid supply port on the liquid flow path side to be W3 greater than xcex1.
Further, it is preferable to arrange the relationship between the overlapping width W4 of the movable member in the discharge port direction overlapping with the opening edge of the liquid supply port on the liquid flow path side, and the overlapping width W3 of the movable member in the widthwise direction to be W3 greater than W4.
The present invention also provides a liquid discharge apparatus which comprises a liquid discharge head structured as described above, and recording medium carrying means for carrying a recording medium receiving liquid discharge from the liquid discharge head. With this liquid discharge apparatus, it is conceivable to discharge ink from the liquid discharge head for recording by the adhesion of the ink to the recording medium.
Also, the method of the present invention for manufacturing a liquid discharge head, which is provided with a plurality of discharge ports for discharging liquid; a plurality of liquid flow paths communicated always with each of the discharge ports at one end, each having bubble generating area for creating bubble in liquid; bubble generating means for generating energy to create and grow the bubble; a plurality of liquid supply ports each arranged for each of the liquid flow paths to be communicated with common liquid supply chamber; and movable member supported with minute gap to the liquid supply port on the liquid flow path side, and provided with free end, the area of the movable member surrounded at least by the free end portion and both sides continued therefrom being made larger than the opening area of the liquid supply port facing the liquid flow path, comprises the steps of forming and patterning a first protection layer with respect to the area covering the portion of the elemental base plate provided with the bubble generating means becoming the liquid flow path; forming a first wall material used for the formation of the liquid flow path on the surface of the elemental base plate including the first protection layer; removing the portion of the first wall material becoming the liquid flow path; burying the portion of the first wall material becoming the removed liquid flow path; smoothing the entire surface of the first wall material by polishing; forming a second protection film on the smoothed first wall material for the formation of a fixing portion for the first wall material and the movable member; forming by patterning the material film becoming the movable member in a smaller width than the portion becoming the liquid flow path on the location corresponding to the portion becoming the liquid flow path; forming on the circumference of the material film becoming the movable member a gap formation member to form a gap between the movable member and the liquid supply port; forming on the first wall material a second wall material for the formation of the liquid supply port on the base plate including the gap formation member; forming the portion of the second wall material becoming the liquid supply port so as to make the opening area thereof smaller than the material film becoming the movable member; removing by resolving the first protection layer used for burying the gap formation member, the second protection layer, and the portion of the first wall material becoming the liquid flow path; and bonding the ceiling plate provided with the common liquid supply chamber to the base plate produced in the steps up to the previous stage.
Also, the method structured as described above for manufacturing a liquid discharge head, which is provided with a plurality of discharge ports for discharging liquid; a plurality of liquid flow paths communicated always with each of the discharge ports at one end, each having bubble generating area for creating bubble in liquid; bubble generating means for generating energy to create and grow the bubble; a plurality of liquid supply ports each arranged for each of the liquid flow paths to be communicated with common liquid supply chamber; and movable member supported with minute gap to the liquid supply port on the liquid flow path side, and provided with free end, the area of the movable member surrounded at least by the free end portion and both sides continued therefrom being made larger than the opening area of the liquid supply port facing the liquid flow path, comprises the steps of forming and patterning a first protection layer with respect to the portion of the ceiling plate becoming the walls of the liquid flow path; forming on the portion of the ceiling plate having none of the first protection layer a gap formation member for the formation of a gap between the movable member and the liquid supply port; forming the material film becoming the movable member on the entire surface of the first protection layer and the gap formation member; forming the material film becoming the movable member with a pattern larger than the opening area of the portion becoming the liquid supply port, and forming through holes on the movable member to facilitate flowing in liquid to resolve the gap formation member; forming by dry etching the common liquid supply chamber with the gap formation member as etching stop layer; removing the gap formation member; forming the liquid supply port by wet etching anisotropically the portion of the ceiling plate having none of the first protection layer; burying the through holes of the movable member with the same material as the material film becoming the movable member, and coating with the film the walls on the etching side; bonding the elemental base plate provided with the wall member for the formation of the liquid flow path and the bubble generating means to the member produced in the steps up to the previous stage.
With the structure described above, the movable member cuts off immediately the communicative condition between the liquid flow path and the liquid supply port during the period from the application of driving voltage to the bubble generating means to the termination of substantially isotropical growth of bubble by the bubble generating means. As a result, the waves of pressure exerted by the bubble growth in the bubble generating area is not propagated to the liquid supply port side and the common liquid supply chamber side. Most of all the pressure is directed toward the discharge port side. Thus, the discharge power is enhanced remarkably. Also, even when a highly viscous recording liquid is used for a higher fixation on a recording sheet or the like or used for the elimination of spreading on the boundary between black and other colors, it becomes possible to discharge such liquid in good condition due the remarkable enhancement of discharge power. Also, the environmental changes at the time of recording, particularly, under the environment of lower temperature and lower humidity, the overly viscous ink region tends to increase, and in some cases, ink is not normally discharged when beginning its use. However, with the present invention, it is possible to perform discharging in good condition form the very first shot. Also, with the remarkably improved discharge power, the size of the heat generating element that serves as bubble generating means can be made smaller or the input energy can be made smaller.
Also, along with the shrinkage of bubble, the movable member is displaced downward to enable liquid to flow from the common liquid supply chamber into the liquid flow path in a large quantity at a rapid flow rate through the liquid supply port. In this manner, the flow that draws meniscus into the liquid flow path is quickly reduced after the droplet is discharge, and the amount of meniscus retraction is made smaller at the discharge port accordingly. As a result, the meniscus returns to the initial state in an extremely short period of time. In other words, the replenishment of a specific amount of ink into the liquid flow path (refilling) is very quick, hence remarkably enhancing the discharge frequency (driving frequency) when executing highly precise ink discharge (in a regular quantity).
Further, in the bubble generating area, the bubble growth is large on the discharge port side, while suppressing the growth thereof toward the liquid supply port side. Therefore, bubble extinction point is positioned on the discharge port side from the central portion of the bubble generating area. Then, while maintaining the discharge power, it becomes possible to reduce the power of bubble extinction. This makes it possible to protect the heat generating member from being mechanically and physically destructed by the bubble extinction in the bubble generating area, and contribute to improving its life significantly.
Also, the foot supporting member is integrally formed with the movable member to support the foot of the movable member, which is provided with a step so that the height position of the movable member is deviated by one step from the fixing position of the foot supporting member. With this arrangement, when the movable member is displaced, the concentration of stress on the fixing position of the foot supporting member of the movable member is relaxed. Further, the thickness of the movable member is made larger than the stepping amount of the foot supporting member of the movable member, hence making it possible to enhance the durability of the foot portion of the movable member, because the concentration of stress is relaxed when it is concentrated on the stepping portion of the foot supporting member of the movable member when the movable member is displaced.
Further, the relationship between the gap a between the opening edge of the liquid supply port on the liquid flow path side and the face of the movable member on the liquid supply port side, and the overlapping with W3 of the movable member in the widthwise direction, is overlapped with opening edge of the liquid supply port on the liquid flow path side is established to be W3 greater than xcex1. Thus, as compared with the case where this relationship is W3 less than xcex1, the flow resistance becomes greater in the flow from the liquid flow path to the liquid supply port side to make it possible to effectively suppress the flow from the liquid flow path to the liquid supply port side at the bubble initiation of the bubble growth. Further, it is possible to effectively suppress the flow from the liquid flow path into the liquid supply port through the gap between the movable member and the circumference of the liquid supply port. As a result, the movable member is able to shield the liquid supply port reliably and quickly. With this operation, the discharge efficiency is enhanced still more.
Also, the relationship between the overlapping width W4 of the movable member in the discharge port direction, which is overlapped with the opening edge of the liquid supply port on the liquid flow path side, and the overlapping width W3 in the widthwise direction of the movable member is established to be W3 greater than W4. With this arrangement, the contact width between the free end tip of the movable member and the opening edge of the liquid supply port becomes smaller when the movable member, which has been displaced upward to the liquid supply port side by the initial bubbling, begins to be displaced downward to the bubble generating means side in the process of the bubble extinction. As a result, the friction force that may be generated at that time is reduced to make it possible to release the liquid supply port priorly from the free end side of the movable member. This makes the releasing of the liquid supply port by the movable member reliably and quickly. Consequently, refilling into the liquid flow path is carried out more efficiently to stabilize the discharge characteristics.
Also, with the adoption of thin film of amorphous alloy for the cavitation proof film on the uppermost surface layer of bubble generating means, it becomes possible to make its life longer against the mechanical and physical destruction.
Also, in the manufacturing processes of the liquid discharge head in accordance with the present invention, the adoption of the amorphous alloy makes it possible to considerably reduce the damages that may be caused to the wiring layer which is arranged on the lower layer even in the removal step whereby to remove the Al film for the formation of the liquid flow path and liquid supply port as well. This contributes significantly to enhancing the production yield.
The other effects and advantages of the present invention will be understandable from the description of each embodiment which is given below.
In this respect, the terms xe2x80x9cupstreamxe2x80x9d and xe2x80x9cdownstreamxe2x80x9d used for the description of the present invention are the expressions to indicate the liquid flow in the direction toward the discharge port from the supply source of liquid through the bubble generating area (or through the movable member) or to indicate the direction on the structural aspect thereof.
Also, the term xe2x80x9cdownstream sidexe2x80x9d of bubble itself means the downstream side of the center of the bubble in the aforesaid flow direction or the aforesaid structural direction, or it means the bubble to be created on the area on the downstream side of the central area of the heat generating element.
Also, the term xe2x80x9coverlapping widthxe2x80x9d indicates the minimal distance from the opening edge of the liquid supply port on the liquid flow path side to the edge portion of the movable member.
Also, the expression xe2x80x9cthe movable member closes and essentially cuts off the liquid supply portxe2x80x9d used for the present invention does not mean that the movable member is necessarily in contact closely with the circumference of the liquid supply port, but it means to include a condition where the movable member approaches the liquid supply port as close as possible.